There are no "events" in the Chancellor's Mansion, just treasure and a learnable skill.

But, since the mansion is now open, this is a good time to check it out.

When you're done here, go to Pican Port and talk to the Sailor to travel to the Kingdom of Tenebrant.

Map and treasure list by Searinox119

Treasure

T1 - Maid's Brew x2
T2 - Leather Bustier
T3 - INT Seed x6
T4 - Life Seed
T5 - Light Rod +20 (Paralysis 12% Confusion 12% Swoon 6% Idle 20%)
T6 - Light Knuckle +18 (SPD 16% MP 20% SP 6%)

Learnable Skill

Talk to the Wandering Maid in the room where you find the Life Seed, and she'll teach you Miracle Body.

Learnable Skill Reward

Talk to the Wandering Maid. If you learned her skill in your first playthrough, she'll give you Life Seed x8.